Design strategies for multifunctional magnesium alloy coatings in marine environments: Coupling corrosion resistance, superhydrophobicity and antifouling

Magnesium alloys are increasingly attractive for marine applications due to their low density and high specific strength; however, their inherent susceptibility to corrosion and biofouling severely restricts long-term performance. The simultaneous integration of corrosion resistance, superhydrophobicity and antifouling qualities has been made possible by recent developments in multifunctional coating design. This review systematically summarizes the design strategies of magnesium-based composite coatings, including plasma electrolytic oxidation, sol-gel, hydrothermal and bioinspired hybrid systems with particular emphasis on their structure-property relationships. Special consideration is given to the synergistic interplay between micro/nano hierarchical architectures and low-surface-energy modifications, which collectively strengthen barrier performance, reduce wettability, and inhibit biological adhesion in marine environments. The novelty of this review lies in establishing a unified framework that correlates these functionalities, highlighting their interdependence rather than treating them as independent attributes. Furthermore, critical challenges related to coating durability, mechanical robustness and long-term stability under dynamic marine conditions are discussed. Finally, future perspectives are outlined for the development of smart, self-healing and environmentally sustainable coating systems for next-generation magnesium-based marine applications.